The present invention relates to the field of wireless communications. One of the applications of the present invention is directed to a downlink signaling approach employing a modified cyclic redundancy check for both data protection and unique/group UE identification.
Wireless communication systems have become an integral link in today's modern telecommunications infrastructure. As such, they have become increasingly relied upon not only to support voice communications, but also data communications. Voice communications are relatively low-rate, symmetrical in the upstream and downstream bandwidths and are predictable in the amount of bandwidth required.
However, data communications can place severe burdens upon a telecommunication system, particularly a wireless telecommunication system. First, data communications can often require extremely high data rates. Second, the amount of bandwidth for a data related application can vary greatly from several kilohertz of bandwidth to several megahertz. Third, the amount of bandwidth in the upstream and downstream directions can be drastically different. For example, with a typical Internet browsing application, very little data is sent in the upstream direction while vast amounts of data are downloaded in the downstream direction. These factors can place severe constraints upon a wireless telecommunication system.
The Wideband CDMA (WCDMA) standard, as the leading global third generation (3G) (IMT-2000) standard, supports data rates up to 2 Mb/s in indoor/small-cell-outdoor environments and up to 384 kb/switch wide-area coverage, as well as support for both high-rate packet data and high-rate circuit-switched data. However to satisfy the future demands for packet-data services, there is a need for a substantial increase in this data rate, especially in the downlink. High speed downlink packet access (HSDPA) would allow WCDMA to support downlink peak data rates in the range of approximately 8-10 Mb/s for best-effort packet-data services. This rate is far beyond the IMT-2000 requirement of 2 Mb/s. It also enhances the packet-data capability in terms of lower delay and improved capacity.
One solution for supporting data communications is the allocation of dedicated channels to each user equipment (UE). However, this results in an extremely inefficient use of the bandwidth since such channels often remain idle for long durations.
An alternative to dedicated channels for each UE is the use of the high speed shared data channels and the packeting of data. In this method, a plurality of high speed data channels are shared between a plurality of UEs. Those UEs having data for transmission or reception are dynamically assigned one of the shared data channels. This results in a much more efficient use of the spectrum.
One such process for assigning a high speed shared data channel when a base station has data waiting for transmission to a particular UE is shown in FIGS. 1A-1C. Referring to FIG. 1A, an associated downlink dedicated physical channel (DPCH) is transmitted to each UE. The UE monitors associated downlink DPCH as well as the shared control channels (SCCH-HS). When there is no data being transmitted to the UE from the base station, the UE enters a standby mode whereby it periodically “wakes up” to attempt to monitor its associated downlink DPCH as well as SCCH-HSs. This permits the UE to save processing and battery resources.
If data at the base station is ready for transmission to the UE, a High Speed Downlink Shared Channel (HS-DSCH) indicator (HI) is transmitted in the associated DPCH. The HI has n-bit length, which points to one of 2n SCCH-HSs shown in FIG. 1B. For example a 2 bit HI can point to 4 SCCH-HSs, i.e., 00, 01, 10 or 11.
For the example shown in FIG. 1A, the HI is (1, 0) which points to the third channel shown in FIG. 1B. When the UE accesses the control channel identified by the HI, that particular SCCH-HS will direct the UE to the proper HS-DSCH, which has been allocated to the UE for reception of the data. As shown in FIG. 1C, for example, the UE tunes to HS-DSCH (001) that was identified by SCCH-HS (1, 0). The UE then receives the data intended for it over the HS-DSCH (001). It should be noted that the graphical representation of FIG. 1A-1C has been presented to illustrate the process of assigning HS-DSCHs, and the configuration and use of channels may differ slightly from actual implementation in HSDPA standards.
The process as described with reference to FIGS. 1A-1C provides an efficient method for assigning common data channels for transmission of data. Since packet data is intended for one or more, specific UEs, the UE identity (ID) is a critical parameter for signaling from the base station to the UE.
There are several prior art methods for signaling the UE ID between the base station and the UE. Referring to FIG. 2A, the first method appends the UE ID onto the data for transmission. The combination is fed to a cyclic redundancy check (CRC) generator, which outputs a CRC. The resulting data packet, which is ultimately transmitted, includes an X-bit data field, an M-bit UE ID and an N-bit CRC as shown in FIG. 2B. Although this provides adequate signaling of both the CRC and the UE ID, it is wasteful of signaling bandwidth.
Another prior art technique shown in FIG. 3A appends the UE ID onto the data field for input into the CRC generator. The CRC generator outputs a CRC. As shown in FIG. 3B, the data burst for transmission includes an X-bit data field and an N-bit CRC field. Although this also adequately signals the UE ID and the CRC between the base station and the UE, it is undesirable since it can only be used for unique UE identification. This method also causes increased complexity of the UE when a group of UEs need to be identified.